The continuing thrust of our research effort is to understand the biochemistry, physiology and nutrition of iron and other trace elements, particulary copper, zinc and manganese. Trace element requirements, homeostasis, and ultimate functions have been meticulously reviewed. However, the detailed events at the cell membrane and within cells which determine the availability of the elements to their respective enzymes and/or tissues has not been documented. We seek to elucidate the specific mechanisms involved in the absorption, storage, utilization and excretion of trace metals from mammalian systems. Our goal is to explain iron and other trace element metabolism in terms of the solution chemistry of the metal ions, their interaction, and the biochemistry of specific metal binding and transporting proteins and low-molecular weight ligands. Our commitment is to apply this knowledge both to the detection and prevention of pathological and nutritional disorders of trace element metabolism. There are four main aspects of our continuing studies: 1. To define the mechanism of interaction among trace elements during dietary assimilation. 2. To study the effect of low-molecular weight ligands on the mechanism of transmembrane transport of iron and other trace metals. Particular attention will be given to the ability of these chelating agents to "steer" trace elements to specific tissues. 3. To determine the potential interrelationships of copper and ascorbic acid in the regulation and control of iron metabolism. 4. To study the biological mechanisms whereby ferric (III) iron may be reduced to ferrous (II) iron under aerobic conditions. 5. To continue our collaborative studies on the nutrition of iron and copper fortification of school lunch programs in Durango, Mexico.